The present invention relates to an image display apparatus and an image display method, and a driving apparatus and a driving method, and particularly to an image display apparatus and an image display method, and a driving apparatus and a driving method that make it possible to display an image using a display element and measure the modulation characteristics of the display element efficiently.
In recent years high resolution is increasingly required in for example introducing a new broadcasting system, increasing an image processing speed with an advance of an arithmetic operation device, and converting a mode in related art of projecting an image in a magnified form using a film (so-called analog cinema) to a mode utilizing digital signal processing (digital cinema). It is difficult for two-dimensional display elements such as a liquid crystal light valve and the like to keep pace with such a tendency for higher resolution because of drawbacks of the two-dimensional display devices result from an increase in the number of pixels and a reduction in pixel size.
For example, when resolution is to be heightened by increasing the (total) number of pixels while fixing the size of a display element, the opening portion of a display part cannot help being reduced in size, so that brightness is sacrificed (it is difficult to realize a bright projector apparatus). On the other hand, when resolution is to be heightened while pixel size is fixed, a drawback occurs in that the size of the display element is inevitably increased, thus resulting in an increase in size and cost of an apparatus including an optical system.
Incidentally, a reduction in pixel size requires a measure to prevent smaller foreign substances from being mixed into the display element in a process of manufacturing the display element. An increase in size of the display device requires an increase in size of a manufacturing apparatus itself.
Thus, when an arrangement in which scanning is performed in a predetermined direction using a one-dimensional display element, it is possible to greatly reduce the number of pixels arranged in the element.
As an example, a high-resolution television or a high-definition television, that is, a so-called HDTV (High Definition TeleVision) using a two-dimensional display element requires a number of elements corresponding to 1920×1080≈2.07 million pixels, whereas a system that performs scanning in a horizontal (H) direction using a one-dimensional display element can be realized with a number of elements corresponding to 1080 pixels. Therefore the superiority of the latter is obvious.
Accordingly, a technique for achieving higher resolution using a one-dimensional display element is proposed (for example, see Japanese Patent Laid-open No. 2004-4256, hereinafter Patent Document 1).
According to Patent Document 1, an image is formed by a two-dimensional image forming apparatus (an image display apparatus forming a two-dimensional image from a one-dimensional image) 1 including a light scanning apparatus 1a as shown in FIG. 1.
The light scanning apparatus 1a has a one-dimensional display element 2, a projection optical system 3, and light deflecting means (or a light deflecting apparatus) 4.
The one-dimensional display element 2 is formed by arranging a plurality of light emitting parts or light modulating parts along one direction. The one-dimensional display element 2 is formed by a one-dimensional light emitting display element in which a plurality of light emitting parts are arranged in a line form, or a one-dimensional light modulating element in which a plurality of light modulating parts are arranged in a line form, for example.
A GLV (Grating Light Valve) made by Silicon Light Machines of the U.S., for example, is known as the one-dimensional light modulating element (spatial light modulating element) (see U.S. Pat. No. 5,311,360). This GLV is formed by a phase reflection type diffraction grating formed by making full use of MEMS (Micro ElectroMechanical System) technology. Since the phase reflection type diffraction grating typified by the GLV does not emit light by itself, a light source is necessary (a coherent light source is desirable).
The projection optical system 3 forms a projected image by reflecting light incident from the one-dimensional display element 2, and is a reflection type one-dimensional projection optical system. For example, an Offner optical system disclosed in U.S. Pat. No. 3,748,015 is exemplified as a basic system for unmagnification projection, and reflection is performed three times in this system. That is, the Offner optical system is formed by using a pair of reflectors so that a first reflection and a third reflection are performed on a curved surface having the same center and the same radius of curvature and a second reflection is performed on a different surface.
The light deflecting means 4 is provided to form a two-dimensional image by scanning the light from the projection optical system 3. That is, the light deflecting means 4 provides the two-dimensional image by scanning the outgoing light, which is obtained after the light is reflected by the projection optical system 3 three times or more, in a plane including a direction orthogonal to a direction of arrangement of the light emitting parts or the light modulating parts in the one-dimensional display element 2. A rotary reflector (such as a galvanomirror or the like), for example, is cited as the light deflecting means 4.
The two-dimensional image obtained through the light deflecting means 4 is magnified through a magnifying and projecting system 5, and then projected onto a screen 6. That is, the magnifying and projecting system 5 is an optical system for magnifying and projecting the two-dimensional image obtained by the projection optical system 3 and the light deflecting means 4 using the two-dimensional image as an intermediate image.
Thus, the two-dimensional image is obtained by scanning by the light deflecting means 4 (scanning the light in the direction orthogonal to the direction of arrangement of the light emitting parts or the light modulating parts in the one-dimensional display element 2) in a stage preceding the magnifying and projecting system 5.
Incidentally, the use of the one-dimensional display element having a plurality of light modulating parts arranged in one direction requires a light source for irradiating the one-dimensional display element with light. The two-dimensional image can be obtained by reflecting the light three times or more which light is applied from the light source to the one-dimensional display element and thereafter enters the projection optical system 3, and then scanning the light by the light deflecting means 4 in a plane including a direction orthogonal to a direction of arrangement of the light modulating parts in the one-dimensional display element.
FIG. 2 and FIG. 3 are diagrams of assistance in explaining operating principles of a GLV element as an example of the one-dimensional display element. In FIG. 2, an arrow “I” directed to a substrate 8 shows a direction of incident light, and an arrow “R” going away from the substrate 8 shows a direction of reflected light. In FIG. 3, an arrow “I” directed to the substrate 8 shows an incident direction, an arrow “D+1” shows a direction of +1st order diffracted light, and an arrow “D−1” shows a direction of −1st order diffracted light.
A reflection grating type element has a structure in which a large number of movable gratings 9 (referred to also as ribbon electrodes) and fixed gratings 10 are arranged in a predetermined direction on the substrate 8. Reflective films are formed on the respective surfaces of the movable gratings 9 and the fixed gratings 10 arranged alternately. That is, the movable gratings 9 are arranged as flexible beams (micro bridges) and elastically supported on the substrate, the reflective films 9a are formed on the surfaces of the movable gratings 9, and the reflection films 10a are formed on the fixed gratings 10.
An electrode layer 8b is formed on a surface of the substrate 8 opposite from a surface 8a above which the movable gratings 9 and the fixed gratings 10 are disposed.
In a state in which no potential difference is applied between the movable gratings 9 and the electrode layer 8b, as shown in FIG. 2, the height of the movable gratings 9 is equal to the height of the fixed gratings 10, and thus the heights of the reflective surfaces of the movable gratings 9 and the fixed gratings 10 (distances from the substrate 8) coincide with each other. Therefore no diffracting action occurs. Accordingly, wavefronts Wi, which are shown by broken lines in parallel with the surface 8a, of light incident from the I-direction are reflected in the R-direction as regularly reflected light, that is, as 0th order light.
When a voltage is applied between the movable gratings 9 and the electrode layer 8b, the movable gratings 9 are bent and drawn toward the substrate 8 side by electrostatic attraction, so that an optical path difference can be changed. That is, as shown in FIG. 3 in an exaggerated manner, a reflection and diffraction effect occurs when the potential difference is applied between the movable gratings 9 and the electrode layer 8b such that the depth of the gratings (the difference between the heights of the movable gratings 9 and the fixed gratings 10) is one fourth of a light wavelength λ (λ/4), and the movable gratings 9 are thus made to come closer to the surface 8a of the substrate. The wavefronts Wi of the light incident from the I-direction are emitted as wavefronts Wd+ and Wd− (shown by broken lines whose intervals are shorter than those of the broken lines representing the wavefronts Wi in FIG. 3) of ±1st order diffracted light directed in directions “D+1” and “D−1.”
Thus, regularly reflected light (0th order reflected light) can be obtained in a non-driven state in which no voltage is applied, and diffracted light (1st order diffracted light) can be obtained in a driven state in which a voltage is applied. Therefore light modulation can be performed by controlling these states in each pixel. That is, the phase reflection type diffraction grating can be obtained by controlling the depths of respective movable gratings, which correspond to respective pixels, in correspondence to an image signal.
When the phase reflection type diffraction grating such as the GLV element is used as the one-dimensional display element, it is desirable to dispose a Schlieren aperture for cutting off diffracted light of specific orders included in the diffracted light diffracted by the diffraction grating at a surface (reflection surface) forming the projection optical system 3. When an Offner optical system is employed as the projection optical system 3, for example, a Schlieren aperture can be disposed at a reflection surface for second reflection. Thereby an inexpensive two-dimensional image forming apparatus can be realized by reducing the number of constituent parts as a whole.
In practice, however, it is not easy for the image display apparatus providing 1080×1920 pixels obtained by scanning the GLV including 1080 pixel elements, for example, to achieve excellent image display in all the pixels. This is because it is generally difficult in device manufacturing to fabricate ribbon electrodes forming pixel elements with a uniform shape and a uniform surface state over the entire display area. Thus, projections or depressions on the order of nanometers occur even when the element is not operated. Therefore the GLV as a modulator varies modulation characteristics (driving voltage-modulated light luminance) among different pixel elements. As a result, nonuniformity in luminance appears on a screen, and a uniform black image cannot be obtained, for example.
Further, there are variations in the characteristic itself of a driving circuit provided for each pixel to adjust the gradation of luminance. Therefore it is not easy to make the modulation characteristics of pixel elements uniform. For example, an error of a driving signal for moving ribbon electrodes on the order of nanometers varies an amount of movement of movable ribbon electrodes in a GLV, and hence causes variations in the modulation characteristics of pixel elements. Such variations in the modulation characteristics are perceived as horizontal stripes in a unit of one to several pixels on a display screen, and thus cause deterioration in picture quality.
Accordingly, a technique of detecting nonuniformity of modulation characteristics of a modulation element in advance and correcting a driving signal or the like on the basis of the detected modulation characteristics is proposed (for example, see Japanese Patent Laid-Open No. 2004-157522, hereinafter called Patent Document 2).
According to Patent Document 2, an image display apparatus as shown in FIG. 4 displays an image or detects modulation characteristics. As shown in the figure, a green laser 51G and a blue laser 51B are arranged so as to emit laser light in directions parallel to a page surface of FIG. 4, while a red laser 51R is arranged such that red laser light thereof is orthogonal to the page surface of FIG. 4.
The sectional shape of the light beams from the red laser 51R, the green laser 51G, and the blue laser 51B is converted according to the shape of GLVs 53R, 53G, and 53B as a one-dimensional image element, and then the laser light is applied to the GLVs 53R, 53G, and 53B.
Line generator expanders 71, 75, and 76 each include two optical lenses, and form linear laser light to be applied to the GLVs 53R, 53G, and 53B disposed linearly.
The linear blue laser beam emitted from the line generator expander 71 is converged by a converging lens 73, deflected by a mirror 74, and then condensed on the GLV 53B. The linear green laser beam emitted from the line generator expander 76 is deflected by a mirror 78, converged by a converging lens 79, and then condensed on the GLV 53G. The linear red laser beam emitted from the line generator expander 75 is converged and deflected by a converging lens and a mirror not shown in the figure, and then condensed on the GLV 53R.
In the GLV 53R, the GLV 53G, and the GLV 53B having a function of a spatial modulator, each ribbon electrode of each pixel element is displaced according to a driving voltage applied thereto. The GLV 53R, the GLV 53G, and the GLV 53B thereby modulate the incident laser light, and emit modulated light including diffracted light of even-numbered orders such as 0th order light and ±2nd order light or diffracted light of odd-numbered orders such as ±1st order light and ±3rd order light. The diffracted light of the even-numbered orders or the odd-numbered orders advance in directions determined by the spatial periods of the GLV 53R, the GLV 53G, and the GLV 53B, that is, are spatially modulated by the GLV 53R, the GLV 53G, and the GLV 53B.
The emitted modulated light of the different colors is mixed by a color synthesis unit 54 to form laser light of a desired color. The color synthesis unit 54 includes a first color synthesis filter 54a and a second color synthesis filter 54b. 
The red laser light modulated by the GLV 53R and the green laser light modulated by the GLV 53G are first subjected to color synthesis by the first color synthesis filter 54a. Then, the second color synthesis filter 54b synthesizes the blue laser light modulated by the GLV 53B with the laser light synthesized by the first color synthesis filter 54a. 
The laser light synthesized by the second color synthesis filter 54b is applied to an Offner relay mirror 35a having a concave surface. The Offner relay mirror 35a having the concave surface reflects the applied light to a Schlieren filter 35b having a convex surface. The Schlieren filter 35b formed by a convex mirror is disposed on a Fourier plane of the concave Offner relay mirror 35a. A ratio of a radius of curvature of the Schlieren filter 35b to that of the concave Offner relay mirror 35a is 1:2. The 0th order light, the +2nd order light, and the −2nd order light, or the +1st order light and the −1st order light, and other diffracted light of higher orders reflected by the concave Offner relay mirror 35a are converged at respective different positions on the convex surface of the Schlieren filter 35b. The Schlieren filter 5b removes the diffracted light other than the ±1st order light, and introduces only the ±1st order light to a light diffusion unit 37.
The concave Offner relay mirror 35a reflects, to the convex Schlieren filter 35b, the laser light synthesized by the second color synthesis filter 54b at a reflection angle smaller than that of a reflecting mirror in the form of a flat plate. The convex Schlieren filter 35b reflects, to the Offner relay mirror 35a, the ±1st order light at a reflection angle greater than that of a reflecting mirror in the form of a flat plate. The concave Offner relay mirror 35a reflects, to a mirror 80, the ±1st order light at a reflection angle smaller than that of a reflecting mirror in the form of a flat plate.
The ±1st order light can be extracted without any aberration by the arrangement of the concave Offner relay mirror 35a and the convex Schlieren filter 35b. 
The mirror 80 deflects the modulated light toward the light diffusion unit 37. The light diffusion unit 37 diffuses the laser light incident from the mirror 80 into parallel light having a great width in side elevation and having a small width in top plan. The diffused linear laser light enters a projection lens 55. The projection lens 55 projects the diffused linear laser light onto a scanning mirror 56. The scanning mirror 56 is formed by a galvanomirror, for example. The scanning mirror 56 projects the linear laser light onto a screen 38 in front thereof to form a one-dimensional image formed by a row of pixels. Further, the scanning mirror 56 rotates according to an image signal. The scanning mirror 56 thereby scans such a one-dimensional image on the screen 38 to form a two-dimensional image.
Further, a light detection apparatus 45 is provided between the projection lens 55 and the scanning mirror 56. The light detection apparatus 45 measures the modulated light emitted from the pixel elements of the GLVs to determine modulation characteristics. Also, the light detection apparatus 45 detects nonuniformity in luminance and color displayed on the basis of variations in the modulation characteristics and illumination conditions. The light detection apparatus 45 includes a reflecting mirror 46, an optical sensor 47 formed by for example an integrating sphere or a CCD, and a lens 48 for converging deflected laser light. The lens 48 is interposed between the reflecting mirror 46 and the optical sensor 47.
The reflecting mirror 46 deflects the modulated light emitted from the projection lens 55 toward the optical sensor 47. When an integrating sphere is used, for example, the optical sensor 47 reflects the light input thereto within the integrating sphere so that the input light is not leaked to the outside of the integrating sphere. The optical sensor 47 thereby collects all of the incident light, and measures the energy of the incident light, that is, the light quantity of the incident light. The reflecting mirror 46 is placed at this position only when display nonuniformity is measured in advance, for example, to change the optical path. When an image is displayed actually, the reflecting mirror 46 is removed to restore the normal light path.
In addition, a method of providing a light detection apparatus 97 outside and near a normal optical path 99 for forming a two-dimensional image on a screen 98 as shown in FIG. 5 is proposed (for example, see WO2004/004167 A1, hereinafter called Patent Document 3).
According to Patent Document 3, as shown in FIG. 5, light applied from a light source 92 to a pixel element 94 is reflected by a scanner 96 and then applied to the screen 98. The scanner 96 is formed by a polygon mirror or the like. The scanner 96 rotates to scan a one-dimensional image on the screen 98 and thereby form a two-dimensional image, as in the case of the above-described galvanomirror.
The light detection apparatus 97 is disposed outside and near the normal optical path 99 facing in a direction of the screen 98. The light detection apparatus 97 is formed by a linear detector or the like, which detector is formed by arranging, in a row, photodiodes or the like for receiving light reflected from the scanner 96 and outputting a signal according to the received light. The light detection apparatus 97 measures modulated light emitted from each pixel element to determine modulation characteristics.
Thus, by detecting nonuniformity in modulation characteristics of a modulation element in advance and correcting a driving signal or the like on the basis of the detected modulation characteristics, it is possible to display a two-dimensional image with little degradation.